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0) Prerequisites

  • Python 3.10+ and pip installed
  • A terminal on macOS/Linux/WSL (Windows PowerShell also works)
Tip: Use a virtual environment to keep dependencies isolated: 
python -m venv .venv
source .venv/bin/activate  # macOS/Linux
# .venv\Scripts\activate    # Windows

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1) Create a project folder

mkdir my_project
cd my_project

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2) Install the CLI

pip install componentize-py

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3) Add the WIT world

Create newton-provider.wit in the project root: 
package newton:provider@0.1.0;

interface http {
    record http-request {
        url: string,
        method: string,
        headers: list<tuple<string, string>>,
        body: option<list<u8>>,
    }

    record http-response {
        status: u16,
        headers: list<tuple<string, string>>,
        body: list<u8>,
    }

    fetch: func(request: http-request) -> result<http-response, string>;
}

world newton-provider {
    import http;
    export run: func(input: string) -> result<string, string>;
}

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4) Generate Python bindings

This produces a wit_world package with types and imports for your WIT: 
componentize-py -d newton-provider.wit -w newton-provider bindings py_bindings
Resulting project structure (key parts): 
my_project/
├─ newton-provider.wit
└─ py_bindings/
   ├─ wit_world/           # generated Python bindings
   └─ app.py               # (you will add this file next)

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5) Implement your component logic

Create py_bindings/app.py: 
from json import loads, dumps
import wit_world
from wit_world.imports import http
from wit_world.imports.http import HttpRequest, HttpResponse

# WIT: export run: func(input: string) -> result<string, string>
# We return a JSON string on success AND on "errors"
# (i.e., we don't surface WIT Err<string> — we encode error info in JSON)
class WitWorld(wit_world.WitWorld):
    def run(self, input: str) -> str:
        req = loads(input)
        # do stuff
        output = {"result": "example"}  # replace with your logic
        return dumps(output)
Note: Keep all imports at the top of the file; don’t import inside functions.

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6) Build the component

From inside the py_bindings/ directory, build the component: 
cd py_bindings
componentize-py -d ../newton-provider.wit -w newton-provider componentize --stub-wasi app -o ../policy.wasm
You’ll get policy.wasm in the project root — a component that:
  • Imports newton:provider/http.fetch from the host
  • Exports run(input: string) -> result<string, string>

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7) Next steps

  • Port the op-sim directory (in its entirety) from: op-sim GitHub into your project root.
  • Test your WASM binary by running op-sim: 
cd op-sim
cargo run --release -- ../policy.wasm '<your_input_string>'
# Example:
# cargo run --release -- ../policy.wasm '{"inquiry_id": "inq_xRZrQFKg7rqZ5UZGLhnvb2ympshE"}'